Wordpress is system with a rich ecosystem of plugins. There is a plugin for anything you can imagine, some of them have a cost but most of them are free. Here is my personal list of plugins I used in the last blogs I've built with Wordpress. All of them are FREE and some of theme have a paid version but are fully functional in the free version.
Content editing Wordpress plugins
By SiteOrigin
A drag and drop, responsive page builder that simplifies building your website.
This plugin adds a new way to edit content in your Wordpress. It adds a Page Builder tab that allows you to create posts and page and edit the page layout dividing the content in rows. For each row you can define the number and width proportion of the columns. I love to edit the content directly in HTML with the text tab but, and here it comes the best part of this plugin, this allows you to insert widgets directly in each cell of the layout defined through this plugin.
By SiteOrigin
A collection of all widgets, neatly bundled into a single plugin. It's also a framework to code your own widgets on top of.
This plugin is nothing else than a collection of widgets to add to the previous defined layout. It gives you many common components like Hero Units, blocks for testimonies, slides, grids and carousels to display the content in several ways. All this with an easy editing interface from the Page builder.
By wpinked
A collection of highly customizable and thoughtfully crafted widgets. Built on top of the SiteOrigin Widgets Bundle.
If you don't have enough widgets with the provided with the SiteOrigin bundle, here is another nice widget collections from WpInked.
By Jeff Starr
Display beautiful syntax-highlighted code snippets with Prism.js or Highlight.js
This plugin provides the use of Prism.js library (or Highlight.js ) to format and highlight code in your posts. It provides some themes and support for the most common programming languages. You only have to add a <pre> or/and a <code> block with a language-[yourlanguage] in the class atribute. Essential if you want to show code in your posts in a nice way.
The only cookie consent plugin you'll ever need.
Yes, this site uses cookies too... This plugin adds the mandatory alert and creates a basic page with a legal information about the cookies without pain.
Social sharing and SEO Wordpress plugins
By Automattic
Add AMP support to your WordPress site
Google is trying to "help" the mobile web browsing with the open source initiative AMP improving the page load speed with cached and enhanced content. With this plugin provided by Automattic the AMP pages will be automatically generated.
By Disqus
*The Disqus comment system replaces your WordPress comment system with your comments hosted and powered by Disqus. Head over to the Comments admin page to set up *your Disqus Comment System.
This plugin replaces the default comments system of Wordpress with the comment system provided by Disqus. Disqus allows the user to log with any social account and provides a rich moderation tool for all your web sites in one place.
A simple plugin that enables you to add share buttons to all of your posts and/or pages.
A great plugin to add social sharing buttons in each page or post, easy to configure and provides some nice predefined styles.
By WebKinder
Google Analytics for WordPress without tracking your own visits
Simply adds the Google analytics track code in each page to track the user navigating information.
By Team Yoast
The first true all-in-one SEO solution for WordPress, including on-page content analysis, XML sitemaps and much more.
A helpful plugin that provides some interesting features to enhance the SEO of the sites. It adds social cards to improve the engagement when sharing on social networks and provides a Sitemap generator to help search engines to index the site. The free version allows you to make a SEO analysis of given words and the Premium version allows you multiple analysis per post. THis is maybe the only
Makes sure the default WordPress AMP plugin uses the proper Yoast SEO metadata
This plugin sets the meta information generated with Yoast SEO plugin into the automatic generated AMP pages.
This plugin will generate a special XML sitemap which will help search engines like Google, Yahoo, Bing and Ask.com to better index your blog.
If you don't use the previous plugin, you can use this one. It only generates the sitemap.xml to be provided to search engines for indexing the content.
Wordpress site management plugins
Clone posts and pages.
This plugin helps if you have some "template" pages or posts. Also can be used to create "drafts" of already published posts and pages.
Import posts from an RSS feed.
This plugin is automatically installed when you access the import section in the Tools menu and select this kind of import.
By Ali Irani
Automatically upload and import external images of a post to Wordpress upload directory and media management
This plugin saves time uploading images. You can link external images and it will be automatically uploaded to the media of the current blog. Specially useful used together with the RSS import posts: Take a look at the migration process from Ghost to Wordpress.
This plugin allow to generate a child theme, and all related files
It generates a child theme from an installed one directly without having to upload a hand generated child theme.
Enable replacing media files by uploading a new file in the "Edit Media" section of the WordPress Media Library.
Replace any existing media references with a new media file.
By aihimel
*Manage your file the way you like. You can upload, delete, copy, move, rename, compress, extract files. You don't need to worry about ftp. It is realy simple and *easy to use.
Manage freely the files in your Wordpress without using a ftp client. Very handful with the Child theme generator plugin.
By UpdraftPlus.Com, DavidAnderson
Backup and restore: take backups locally, or backup to Amazon S3, Dropbox, Google Drive, Rackspace, (S)FTP, WebDAV & email, on automatic schedules.
You don't want to lose your work. This is why you should backup your content, plugins and themes. This plugin allows you to make and schedule backup copies easily but you need some technical skills to get the required API keys from your cloud provider for copy the files.
By Automattic
Very fast caching plugin for WordPress.
Improves the site speed by caching the visited content.